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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.hazelcast.org.apache.calcite.schema;

import com.hazelcast.org.apache.calcite.rel.RelCollation;
import com.hazelcast.org.apache.calcite.rel.RelReferentialConstraint;
import com.hazelcast.org.apache.calcite.util.ImmutableBitSet;

import com.hazelcast.com.google.common.collect.ImmutableList;

import com.hazelcast.org.checkerframework.checker.nullness.qual.Nullable;

import java.util.List;

/**
 * Utility functions regarding {@link Statistic}.
 */
public class Statistics {
  private Statistics() {
  }

  /** Returns a {@link Statistic} that knows nothing about a table. */
  public static final Statistic UNKNOWN =
      new Statistic() {
      };

  /** Returns a statistic with a given set of referential constraints. */
  public static Statistic of(@Nullable List referentialConstraints) {
    return of(null, null,
        referentialConstraints, null);
  }

  /** Returns a statistic with a given row count and set of unique keys. */
  public static Statistic of(final double rowCount,
      final @Nullable List keys) {
    return of(rowCount, keys, null,
        null);
  }

  /** Returns a statistic with a given row count, set of unique keys,
   * and collations. */
  public static Statistic of(final double rowCount,
      final @Nullable List keys,
      final @Nullable List collations) {
    return of(rowCount, keys, null, collations);
  }

  /** Returns a statistic with a given row count, set of unique keys,
   * referential constraints, and collations. */
  public static Statistic of(final @Nullable Double rowCount,
      final @Nullable List keys,
      final @Nullable List referentialConstraints,
      final @Nullable List collations) {
    List keysCopy = keys == null ? ImmutableList.of() : ImmutableList.copyOf(keys);
    List referentialConstraintsCopy =
        referentialConstraints == null ? null : ImmutableList.copyOf(referentialConstraints);
    List collationsCopy =
        collations == null ? null : ImmutableList.copyOf(collations);

    return new Statistic() {
      @Override public @Nullable Double getRowCount() {
        return rowCount;
      }

      @Override public boolean isKey(ImmutableBitSet columns) {
        for (ImmutableBitSet key : keysCopy) {
          if (columns.contains(key)) {
            return true;
          }
        }
        return false;
      }

      @Override public @Nullable List getKeys() {
        return keysCopy;
      }

      @Override public @Nullable List getReferentialConstraints() {
        return referentialConstraintsCopy;
      }

      @Override public @Nullable List getCollations() {
        return collationsCopy;
      }
    };
  }
}